Water Storage Containers Exhibiting Reduced Corrosion, and Devices and Methods for Reducing Rate of Corrosion in Water Storage Containers

ABSTRACT

A water storage tank includes: a tank containing water; a roof positioned over the tank; a headspace region formed between the roof and a surface of the water contained in the tank; and a corrosion reduction system. The corrosion reduction system includes (i) a port that enables air to flow out of the water storage tank, and (ii) an active air ventilation system having at least one device configured to facilitate movement of air exterior of the water storage tank into the headspace region. The corrosion reduction system reduces a rate of corrosion of the water storage tank. A method of reducing a rate of corrosion of a water storage tank is also included.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/384,074, filed Sep. 6, 2016, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention is directed to water storage containers thatprovide reduced corrosion rates, and devices and methods of reducingcorrosion rates in storage containers.

Description of Related Art

Elevated storage containers and other large water storage containers arean integral part of many municipal water distribution systems. Thesecontainers are intended to ensure adequate hydrostatic pressure toenable effective water delivery and to store water hygienically. Waterstorage tanks also provide relief from water surges and provideemergency supplies for fire and other emergencies. As components ofmunicipal water systems, these containers are expected to have long,useful lives, often from 15 to 25 years, or 50 years or greater.

Achievement of the expected long lifespans of water storage tanks ismade difficult by the very nature of their structure and function. Forexample, water storage tanks are often made of steel, which is subjectto corrosion that will eventually cause failure of the storage tanks.Water storage tanks may be particularly susceptible to corrosion becauseinterior tank temperatures are often in excess of exterior airtemperatures in that the steel (or concrete) structure absorbs heat fromthe sun and re-radiates the heat into the interior of the tank and, witha volume that holds large amounts of water, the interior humidity (“RH”)inside a water storage tank is almost always approaching 100%.Furthermore, the drinking water (and water held for other processes) isoften treated with disinfectant chemicals, such as chlorine, thatproduce vapors which can also accelerate corrosion rates.

Forced air ventilation is a process of controlling the interior humidityof enclosed structures (buildings, storage vessels). However, whencontrolling interior conditions to lower rates of corrosion, it hascommonly been assumed that ventilating exterior atmosphere into anenclosed structure is counter-productive. For example,corrosion-susceptible equipment is commonly stored in an enclosure thatprevents the ingress of outside air. In extreme cases (e.g. the storageof military equipment in tropical climates), structures are built thatinclude active de-humidification.

Typically, water storage tanks are designed to minimize the exchange ofair with the outside. However, it is appreciated that at least some airmust be exchanged as water levels rise or fall within the tank (forexample in order to prevent de-pressurization of the tank duringdraining and buckling of the tank structure). Beyond permitting theminimum amount of air required to equilibrate air pressure inside thetank, no further ventilation is desired.

A common approach to controlling corrosion of water storage tanks is tocoat the interior surfaces of the water storage tanks with epoxy paintsto prevent direct exposure of the steel to corrosion-inducingconditions. However, 100% coverage with no gaps is essentiallyimpossible to achieve. Even if a complete epoxy coating is achieved, thecoating will be subject to stresses due to thermal cycling of thestructure which will produce cracks in the coating, thereby allowing theunderlying steel to become exposed to air or water that causescorrosion. Similarly, VOC-compliant coatings are not as resilient andmust be reapplied more frequently. Coating performance has also beenreduced by the requirements to remove toxic materials, such as lead,from the coatings. Thus, coating failure is a common problem in waterstorage containers and reapplication on a regular basis of thesecoatings is necessary.

Further, reapplication of a coating during tank interior refurbishmentis prone to even greater potential for gaps. For example, tight cornersand areas where roof panels rest atop beams, but which are notseal-welded, are not accessible for recoating and are susceptible tocorrosion. Moreover, the ideal time to reapply the coating materials isin the summer months such that routine maintenance is necessary just atthe time the water storage tanks are needed most.

It is also appreciated that not all surfaces are subjected to the sameconditions. Most facilities focus on protection of water storage tankinteriors where liquid water is in contact with the surface. The bestcoatings to protect water container interior surfaces from corrosionwhere liquid water is in contact are not necessarily the same as thosethat are best to protect surfaces from vapors that contain corrosivechemicals. The areas exposed to chemical vapors is often referred to asheadspace. Further, headspace volume will fluctuate according to theamount of water stored in the tank at various times. Thus, it isdifficult, if not impossible, to apply different coatings to the variousportions of the interior of the water storage tank and achievesatisfactory corrosion protection.

Thus, it is desirable to provide water storage tanks with a reducedpropensity to corrode and which does not require additional maintenanceand costs.

SUMMARY OF THE INVENTION

In certain non-limiting and preferred embodiments, the present inventionis directed to a water storage tank comprising: a tank containing water;a roof positioned over the tank; a headspace region formed between theroof and a surface of the water contained in the tank; and a corrosionreduction system comprising: (i) a port that enables air to flow out ofthe water storage tank; and (ii) an active air ventilation systemcomprising at least one device configured to facilitate movement of airexterior of the water storage tank into the headspace region, in whichthe corrosion reduction system reduces a rate of corrosion of the waterstorage tank.

In some non-limiting and preferred embodiments, the device of the activeair ventilation system is configured to facilitate the movement of airexterior of the water storage tank into the headspace region in adirection that is non-perpendicular to the water surface. The device ofthe active air ventilation system can also be configured to facilitatethe movement of air exterior of the water storage tank into theheadspace region substantially laterally across an interior surface ofthe roof

In certain non-limiting and preferred embodiments, the device of theactive air ventilation system comprises air vent openings that fluidlyconnect the air exterior of the water storage tank to the headspaceregion. The device of the active air ventilation system can furthercomprise at least one screen that is positioned over at least one of theair vent openings.

In some non-limiting and preferred embodiments, the active airventilation system further comprises an air-moving device thatfacilitates an exchange of air between an interior and exterior of thewater storage tank. The active air ventilation system can also comprisea deflector that directs air exterior of the water storage tank into theheadspace region in a direction that is: (i) non-perpendicular to thewater surface; or (ii) substantially laterally across an interiorsurface of the roof. In some non-limiting and preferred embodiments, theactive air ventilation system includes both an air-moving device and adeflector. In such embodiments, the deflector is in fluid communicationwith the air-moving device, and the deflector directs air exterior ofthe water storage tank into the headspace region in a direction that is:(i) non-perpendicular to the water surface; or (ii) substantiallylaterally across an interior surface of the roof.

In certain non-limiting and preferred embodiments, the water storagetank further comprises a mixing device configured to bring cooler waterto a top portion of the tank. Further, at least a portion of the waterstorage tank and/or at least a portion of an interior of the roof can beformed from a material that is prone to corrosion. The material that isprone to corrosion can comprise a metal.

In some non-limiting and preferred embodiments, the corrosion reductionsystem of the present invention reduces the rate of corrosion of thewater storage tank by at least about 10% to at least about 90% asmeasured by ASTM G50-10(2015).

In certain non-limiting and preferred embodiments, the present inventionis also directed to a method of reducing a rate of corrosion of a waterstorage tank comprising actively exchanging air exterior of the waterstorage tank with air inside the water storage tank with a corrosionreduction system to reduce the rate of corrosion of the water storagetank, in which the corrosion reduction system comprises: (i) a port thatenables air to flow out of the water storage tank; and (ii) an activeair ventilation system comprising at least one device configured tofacilitate movement of air exterior of the water storage tank into aheadspace region formed between a roof positioned over the water storagetank and a surface of water contained in the tank.

In some non-limiting and preferred embodiments, the corrosion reductionsystem is retrofitted into the water storage tank. In certainnon-limiting and preferred embodiments, the water storage tank comprisesa mixing device, and the method further comprises actively mixing withthe mixing device such that cooler water is brought to a surface of thewater in the water storage tank. It is appreciated that the waterstorage tank used in the method of the present invention can alsocomprise any of the previously described features.

In certain non-limiting and preferred embodiments, the corrosionreduction system reduces air temperature, humidity, and levels ofoxidizing vapors in the headspace region of the tank. In addition, themethod of the present invention reduces the rate of corrosion of thewater storage tank by at least about 10% to at least about 90% asmeasured by ASTM G50-10(2015).

The present invention is also directed to the following clauses.

Clause 1: A water storage tank comprising: a tank containing water; aroof positioned over the tank; a headspace region formed between theroof and a surface of the water contained in the tank; and a corrosionreduction system comprising: (i) a port that enables air to flow out ofthe water storage tank; and (ii) an active air ventilation systemcomprising at least one device configured to facilitate movement of airexterior of the water storage tank into the headspace region, whereinthe corrosion reduction system reduces a rate of corrosion of the waterstorage tank.

Clause 2: The water storage tank of clause 1, wherein the device of theactive air ventilation system is configured to facilitate the movementof air exterior of the water storage tank into the headspace region in adirection that is non-perpendicular to the water surface.

Clause 3: The water storage tank of clauses 1 or 2, wherein the deviceof the active air ventilation system is configured to facilitate themovement of air exterior of the water storage tank into the headspaceregion substantially laterally across an interior surface of the roof.

Clause 4: The water storage tank of any of clauses 1 to 3, wherein thedevice of the active air ventilation system comprises air vent openingsthat fluidly connect the air exterior of the water storage tank to theheadspace region.

Clause 5: The water storage tank of clause 4, wherein the device of theactive air ventilation system comprises at least one screen that ispositioned over at least one of the air vent openings.

Clause 6: The water storage tank of any of clauses 1 to 5, wherein theactive air ventilation system further comprises an air-moving devicethat facilitates an exchange of air between an interior and exterior ofthe water storage tank.

Clause 7: The water storage tank of any of clauses 1 to 6, wherein theactive air ventilation system comprises a deflector that directs airexterior of the water storage tank into the headspace region in adirection that is: (i) non-perpendicular to the water surface; or (ii)substantially laterally across an interior surface of the roof.

Clause 8: The water storage tank of clause 6, wherein the active airventilation system comprises a deflector that is in fluid communicationwith the air-moving device, and wherein the deflector directs airexterior of the water storage tank into the headspace region in adirection that is: (i) non-perpendicular to the water surface; or (ii)substantially laterally across an interior surface of the roof.

Clause 9: The water storage tank of any of clauses 1 to 8, furthercomprising a mixing device configured to bring cooler water to a topportion of the tank.

Clause 10: The water storage tank of any of clauses 1 to 9, wherein atleast a portion of the water storage tank and/or at least a portion ofan interior of the roof is formed from a material that is prone tocorrosion.

Clause 11: The water storage tank of clause 10, wherein the materialthat is prone to corrosion comprises a metal.

Clause 12: The water storage tank of any of clauses 1 to 11, wherein thecorrosion reduction system reduces the rate of corrosion of the waterstorage tank by at least about 10% to at least about 90% as measured byASTM G50-10(2015).

Clause 13: A method of reducing a rate of corrosion of a water storagetank comprising actively exchanging air outside of the water storagetank with air inside the water storage tank with a corrosion reductionsystem to reduce the rate of corrosion of the water storage tank,wherein the corrosion reduction system comprises: (i) a port thatenables air to flow out of the water storage tank; and (ii) an activeair ventilation system comprising at least one device configured tofacilitate movement of air exterior of the water storage tank into aheadspace region formed between a roof positioned over the water storagetank and a surface of water contained in the tank.

Clause 14: The method of clause 13, wherein the corrosion reductionsystem is retrofitted into the water storage tank.

Clause 15: The method of clauses 13 or 14, wherein the device of theactive air ventilation system is configured to facilitate the movementof air exterior of the water storage tank into the headspace region in adirection that is non-perpendicular to the water surface.

Clause 16: The method of any of clauses 13 to 15, wherein the device ofthe active air ventilation system is configured to facilitate themovement of air exterior of the water storage tank into the headspaceregion substantially laterally across an interior surface of the roof

Clause 17: The method of any of clauses 13 to 16, wherein the active airventilation system further comprises an air-moving device thatfacilitates an exchange of air between an interior and exterior of thewater storage tank.

Clause 18: The method of clause 17, wherein the active air ventilationsystem comprises a deflector that is in fluid communication with theair-moving device, and wherein the deflector directs air exterior of thewater storage tank into the headspace region in a direction that is: (i)non-perpendicular to the water surface; or (ii) substantially laterallyacross an interior surface of the roof

Clause 19: The method of any of clauses 13 to 18, wherein the waterstorage tank comprises a mixing device, and wherein the method furthercomprises actively mixing with the mixing device such that cooler wateris brought to a surface of the water in the water storage tank.

Clause 20: The method of any of clauses 13 to 19, wherein the corrosionreduction system reduces air temperature, humidity, and levels ofoxidizing vapors in the headspace region of the tank.

Clause 21: The method of any of clauses 13 to 20, wherein the methodreduces the rate of corrosion of the water storage tank by at leastabout 10% to at least about 90% as measured by ASTM G50-10(2015).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial front view of a roof portion of a water storage tankhaving a corrosion-reduction system according to a non-limitingembodiment of the invention; and

FIG. 2 is a cross-sectional front view of the anti-corrosion deviceshown in FIG. 1.

DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the followingspecification and attached claims are approximations that may varydepending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

Further, the terms “upper,” “lower,” “right,” “left,” “vertical,”“horizontal,” “top,” “bottom,” “lateral,” “longitudinal,” andderivatives thereof shall relate to the invention as it is oriented inthe drawing figures. However, it is to be understood that the inventionmay assume alternative variations and step sequences, except whereexpressly specified to the contrary. It is also to be understood thatthe specific devices and processes illustrated in the attached drawings,and described in the specification, are simply exemplary embodiments ofthe invention. Hence, specific dimensions and other physicalcharacteristics related to the embodiments disclosed herein are not tobe considered as limiting.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

The phrases “water storage tanks”, “water storage containers”,“water-containing storage tanks” and the like are used interchangeablyand mean the same thing. In addition, the term “water” when used todescribe “water storage tanks/containers” encompasses both water andcompositions comprising water, in which water is the majority of thecomposition.

The present invention relates to systems and methods for reducing therate of corrosion in the headspace region of water-containing storagetanks, such as municipal water storage tanks for example. Although thesystems and methods are non-coating based, the systems and methods ofthe present invention may be used together with coating-based approachesfor reducing the rate of corrosion. As such, the systems and methods ofthe present invention may be used with coating-based water storage tanksor non-coating based water storage tanks. In general, the systems andmethods of the present invention are designed to reduce at least one ofthe temperature, humidity, and levels of oxidizing vapors in theinterior of the water storage tanks, for example by actively exchangingair exterior of the tank with air inside the tank. In some non-limitingand preferred embodiments, the system reduces temperature and humiditylevels in the interior of the water storage tank. In some othernon-limiting and preferred embodiments, the system reduces temperature,humidity and oxidizing vapor levels in the interior of the water storagetank.

The present invention also relates to water-storage tanks, includingmunicipal water-storage tanks, fitted or retrofitted with non-coatingbased corrosion-reduction system that provides a reduced rate ofcorrosion. The corrosion-reduction system is an active ventilationsystem adapted for use with a water storage tank. In certainnon-limiting and preferred embodiments, the active ventilation system isconfigured to move air in a direction that is non-perpendicular to thesurface of the water in the storage tank, which surface defines aboundary of the headspace region. In certain further non-limiting andpreferred embodiments, the active ventilation system is configured tomove air laterally (substantially laterally) across the roof of thewater storage tank.

In some non-limiting and preferred embodiments, the water-containingstorage tank 100 of the present invention is a municipal water storagetank. Municipal water storage tanks typically have a capacity of about500 gallons of water or greater, or about 1000 gallons of water orgreater, or about 100,000 gallons of water or greater, or about1,000,000 gallons of water or greater. Smaller water storage tanks (forexample, having a capacity of 500 gallons or less) may be made fromnon-corrosive materials such as plastic. Larger storage tanks, on theother hand, typically comprise materials that are susceptible tocorrosion such as metal (for example steel). The systems and devices ofthe present invention can be used with water-containing storage tanks100 that are made of various materials including, but not limited to,the previously described materials. The systems and devices of thepresent invention are particularly useful when used withwater-containing storage tanks comprising interior surfaces made atleast partially from materials susceptible to corrosion such as a metal,regardless of whether the surface is protected by a corrosion-resistantcoating.

In certain non-limiting and preferred embodiments, referring to FIG. 1,the water-containing storage tank 100 comprises a headspace region 5formed between a roof portion 3 and the surface of the water containedin the water-containing storage tank 100. As used herein, the term“headspace region” refers to a region in a water-containing storage tank100 that does not contain water. It is appreciated that the volume ofheadspace region 5 fluctuates with respect to the amount of water storedin the water-containing storage tank 100.

The headspace region 5 is particularly vulnerable to corrosion since theinterior conditions inside a water storage tank 100 are often worse (interms of corrosion rates) than conditions outside the tank. For example,interior air temperatures are often greater than exterior airtemperatures because the tank 100 materials (e.g. steel or concrete)absorb heat from the sun and re-radiate the heat into the interior ofthe tank 100. Furthermore, with a volume that holds large amounts ofwater, the interior humidity (“RH”) inside a water storage tank 100 isalmost always approaching 100%. That is, air in the headspace region 5generally exhibits a higher relative humidity than air exterior of thetank 100. The drier exterior air induces vapor flow from the watersurface into the headspace region 5. Because drinking water (and waterheld for other processes) is often treated with disinfectant chemicalssuch as chlorine (a powerful oxidizer), the vapors will includedisinfectant chemicals that further accelerate corrosion rates. Inlocations with low relative humidity and high daytime temperatures, suchas in the U.S. Southwest, it can be expected that corrosion-inducingvapors will be more prevalent because more evaporation will occur underthese conditions. However, it is appreciated that corrosion from watervapors occurs in water-containing storage tanks 100 located in othergeographic regions because, under most environmental conditions,evaporation of water stored in the tank 100 will occur.

In accordance with the present invention, and as shown in FIGS. 1 and 2,the water storage tank 100 is fitted with a corrosion reduction system50 comprising a port 1 and an active air ventilation system 2. As usedherein, a “corrosion reduction system” refers to a system that reducesthe rate of corrosion of a target water storage tank 100. As such,water-containing storage tanks 100 comprising the corrosion-reductionsystems 50 of the present invention exhibit a reduced rate of corrosionas compared to similar water-containing storage tanks 100 without thecorrosion-reduction systems 50. The water storage tanks 100 may beoriginally manufactured with the corrosion-reduction system 50, or maybe retrofitted to include corrosion-reduction systems 50.

Further, the port 1 and an active air ventilation system 2 enter or arein fluid communication with the headspace region 5. For example, and asshown in FIGS. 1 and 2, the port 1 and an active air ventilation system2 are positioned through the roof 3 of the water containing storage tank100 such that the port 1 and the active air ventilation system 2 are influid communication with the headspace region 5.

In general, current water-containing storage tanks 100 are designed tominimize exchange of air to only that which is necessary to equilibratethe air pressure. By contrast, the active air ventilation system 2 ofthe corrosion reduction system 50 of the present invention is configuredto increase ventilation/air access/air exchange beyond that required toequilibrate air pressure in the tank 100, for example by lowering thetemperature, humidity, and/or levels of oxidizing vapors in the interiorof the water storage tank 100.

In some non-limiting and preferred embodiments, the corrosion reductionsystem 50 permits powered introduction of exterior air 6 into theheadspace region 5 of the water storage tank 100. In certainembodiments, the water-storage tanks 100 may exist with installedvolatile organic chemical (“VOC”) reduction devices such as described inU.S. Patent Application Publication No. 2015-0167993, which is herebyincorporated by reference in its entirety, and which may serve thefunction of the air ventilation system 2 for the presentcorrosion-reduction system 50. In some non-limiting and preferredembodiments, the corrosion reduction system includes at least the port1, the active ventilation system 2, and a (re)-configuration of theactive ventilation system 2 to reduce the rate of corrosion as comparedto a water storage tank having only the VOC device installed. Forexample, the rate of corrosion may be reduced by modifying the angle atwhich the VOC device is installed and/or including a deflector 4 asshown in FIG. 2 with the corrosion reduction system 50 to direct airflowfrom exterior of the tank 100 into the headspace region 5 in a directionthat is non-perpendicular to the surface of the water in the tank 100.In some non-limiting embodiments, air is directed from the exteriorlaterally along the interior surface 12 of the roof of the tank 100.

In certain non-limiting and preferred embodiments, and referring to FIG.2, the corrosion reduction system 50 includes an active ventilationsystem 2. The active ventilation system 2 is configured to control oneor more parameters influencing air exchange including airflow rate,airflow direction, and frequency of active exchange (e.g., constant orintermittent) and, contrary to current teachings and understandings, theactive ventilation system 2 is configured to increase ventilation/airaccess/air exchange beyond that required to equilibrate air pressure inthe tank, for example by lowering the temperature, humidity, and/orlevels of oxidizing vapors in the interior of the water storage tank. Insome non-limiting embodiments for example, the active ventilation system2 is configured to accomplish at least approximately 5 to 10 airexchanges/day. For example, for a 1 MG tank with approximately 15 feetof headspace, a minimum of 5 to 10 air exchanges per day wouldcorrespond to 250 to 500 cfm.

Referring to FIG. 2, the active ventilation system 2 comprises aventilation device 8, which impacts airflow rate and frequency, andoptionally a deflector 4, which impacts airflow direction. Theventilation device 8 is configured to facilitate exchange of airexterior 6 to the water storage tank 100 with air interior to the waterstorage tank 100 by fluidly connecting the interior headspace region 5with the exterior environment by way of air vent openings 9. Toalleviate and/or prevent contamination of water stored within the tank100, for example to alleviate or prevent ingress of animals, leavesand/or other debris into the tank 100, screens 10 may be provided tocover the vent openings 9. In addition, the active ventilation system 2is an “active” system, and accordingly provides input energy (e.g.mechanical or electrical) to assist the air exchange process. In certainnon-limiting and preferred embodiments, the input energy is provided byan air-moving device 11 such as a fan. In some non-limiting embodiments,for example where there may be a desire to achieve additional energysavings, a humidity switch may be included which automatically shuts offthe air-moving device 11 if the interior humidity falls below apre-determined amount such as below 100%.

The air-moving device 11 specifications and the dimensions of the airventilation device 8, including the relative dimensions of the airventilation device 8 as compared to the air-moving device 11, determinethe airflow rate (or range of airflow rates). It is appreciated that theangle of the device 8 connected to the water storage tank 100 relativeto the surface of water defining the lower boundary of the headspaceregion 5 will impact airflow direction. Although the air-moving device11, in this example a fan, is shown in FIG. 2 mounted within theventilation device 8 formed on the roof 3 of the water storage tank 100,it need not be mounted on the roof 3 or in the device 8, but, forexample, could be ducted from the ground.

In certain non-limiting and preferred embodiments, a deflector 4 may beused in connection with the air ventilation device 8 to control theairflow direction. The use of a deflector 4 may be desirable where theairflow direction is otherwise perpendicular to the water surface 12.Generally, the rate of corrosion is reduced as the direction of airflowis closer to lateral movement across the interior surface 12 of the roof3 of the water storage tank 100.

In use, and without wishing to be bound by theory, thecorrosion-reduction systems 50 according to the present invention lowersthe temperature, humidity, and/or oxidizing vapor levels by activeventilation alone (exchanging tank air with the exterior air), or bycombining active ventilation with active mixing (not shown) (whichbrings cooler water to the surface of the water in the tank 100,lowering air temperature and humidity levels), or by active mixing alone(which lowers the headspace region 5 temperature by bringing coolerwater to the surface). That is, the corrosion-reduction systems 50according to the present invention, reduce the propensity of theinterior surface of the water storage tank 100 at the headspace region 5to corrode, for example by engaging an air-moving device 11 that is influid communication with the interior and the exterior of the tank 100to circulate air within the headspace region 5, thereby reducing therelative humidity of the headspace region 5 and/or enabling at leastsome of the corrosion-inducing vapors to exit through one or more ports1 positioned in the headspace region 5 (for example the upper portion ofthe headspace region 5), where the one or more ports 1 serve to ventvapors from the headspace region 5 to the exterior of the water storagetank 100 and/or to charge the headspace region 5 with exterior air,which may serve to reduce the concentration of corrosion-inducing vaporsin the headspace region 5. Such lower concentration of vapors (and lowertemperature) results in a reduced rate of corrosion of the exposedcorrosion-susceptible materials in the headspace region 5.

Consequently, the present invention provides water storage tanks 100that exhibit reduced corrosion rates as compared to those not configuredas described herein. In some non-limiting embodiments, the water storagetanks 100 exhibit a rate of corrosion in the headspace region 5 that ismarkedly less than that seen in water storage tanks 100 that do notinclude the features of the present invention. As such, the presentinvention can reduce the rate of corrosion by at least 10%, or at least15%, or at least 20%, or at least 25%, or at least 30%, or at least 40%,or at least 50%, or at least 60%, or at least 70%, or at least 80%, orat least 90% as compared to water storage tanks 100 that do not includethe features of the present invention. As used herein, the rate ofcorrosion is measured by AST G50-10(2015), Standard Practice forConducting Atmospheric Corrosion Tests on Metals, ASTM International,West Conshohocken, Pa., www.astm.org (retrieved Mar. 26, 2016), thedisclosure of which is hereby incorporated in its entirety herein byreference.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

The invention claimed is
 1. A water storage tank comprising: a tankcontaining water; a roof positioned over the tank; a headspace regionformed between the roof and a surface of the water contained in thetank; and a corrosion reduction system comprising: (i) a port thatenables air to flow out of the water storage tank; and (ii) an activeair ventilation system comprising at least one device configured tofacilitate movement of air exterior of the water storage tank into theheadspace region, wherein the corrosion reduction system reduces a rateof corrosion of the water storage tank.
 2. The water storage tank ofclaim 1, wherein the device of the active air ventilation system isconfigured to facilitate the movement of air exterior of the waterstorage tank into the headspace region in a direction that isnon-perpendicular to the water surface.
 3. The water storage tank ofclaim 1, wherein the device of the active air ventilation system isconfigured to facilitate the movement of air exterior of the waterstorage tank into the headspace region substantially laterally across aninterior surface of the roof.
 4. The water storage tank of claim 1,wherein the device of the active air ventilation system comprises airvent openings that fluidly connect the air exterior of the water storagetank to the headspace region.
 5. The water storage tank of claim 4,wherein the device of the active air ventilation system comprises atleast one screen that is positioned over at least one of the air ventopenings.
 6. The water storage tank of claim 1, wherein the active airventilation system further comprises an air-moving device thatfacilitates an exchange of air between an interior and exterior of thewater storage tank.
 7. The water storage tank of claim 1, wherein theactive air ventilation system comprises a deflector that directs airexterior of the water storage tank into the headspace region in adirection that is: (i) non-perpendicular to the water surface; or (ii)substantially laterally across an interior surface of the roof.
 8. Thewater storage tank of claim 6, wherein the active air ventilation systemcomprises a deflector that is in fluid communication with the air-movingdevice, and wherein the deflector directs air exterior of the waterstorage tank into the headspace region in a direction that is: (i)non-perpendicular to the water surface; or (ii) substantially laterallyacross an interior surface of the roof
 9. The water storage tank ofclaim 1, further comprising a mixing device configured to bring coolerwater to a surface of the water in the water storage tank.
 10. The waterstorage tank of claim 1, wherein at least a portion of the water storagetank and/or at least a portion of an interior of the roof is formed froma material that is prone to corrosion.
 11. The water storage tank ofclaim 10, wherein the material that is prone to corrosion comprises ametal.
 12. The water storage tank of claim 1, wherein the corrosionreduction system reduces the rate of corrosion of the water storage tankby at least about 10% to at least about 90% as measured by ASTMG50-10(2015).
 13. A method of reducing a rate of corrosion of a waterstorage tank comprising actively exchanging air exterior of the waterstorage tank with air inside the water storage tank with a corrosionreduction system to reduce the rate of corrosion of the water storagetank, wherein the corrosion reduction system comprises: (i) a port thatenables air to flow out of the water storage tank; and (ii) an activeair ventilation system comprising at least one device configured tofacilitate movement of air exterior of the water storage tank into aheadspace region formed between a roof positioned over the water storagetank and a surface of water contained in the tank.
 14. The method ofclaim 13, wherein the corrosion reduction system is retrofitted into thewater storage tank.
 15. The method of claim 13, wherein the device ofthe active air ventilation system is configured to facilitate themovement of air exterior of the water storage tank into the headspaceregion in a direction that is non-perpendicular to the water surface.16. The method of claim 13, wherein the device of the active airventilation system is configured to facilitate the movement of airexterior of the water storage tank into the headspace regionsubstantially laterally across an interior surface of the roof
 17. Themethod of claim 13, wherein the active air ventilation system furthercomprises an air-moving device that facilitates an exchange of airbetween an interior and exterior of the water storage tank.
 18. Themethod of claim 17, wherein the active air ventilation system comprisesa deflector that is in fluid communication with the air-moving device,and wherein the deflector directs air exterior of the water storage tankinto the headspace region in a direction that is: (i) non-perpendicularto the water surface; or (ii) substantially laterally across an interiorsurface of the roof.
 19. The method of claim 13, wherein the waterstorage tank comprises a mixing device, and wherein the method furthercomprises actively mixing with the mixing device such that cooler wateris brought to a surface of the water in the water storage tank.
 20. Themethod of claim 13, wherein the corrosion reduction system reduces airtemperature, humidity, and levels of oxidizing vapors in the headspaceregion of the water storage tank.
 21. The method of claim 13, whereinthe method reduces the rate of corrosion of the water storage tank by atleast about 10% to at least about 90% as measured by ASTM G50-10(2015).